When a pulse-width modulated (PWM) signal is regulated with the aid of a characteristics map (F), a manipulated variable (t) is set as a function of a controlled variable (R), there being a functional relationshipt=F(R).
In the event of hardware implementation, so that no software algorithm is used for computing t, the values F(RN) are normally reserved for a fixed number of interpolation points N and, for all intermediary values, F(R) is set to the value of the adjacent interpolation point or an intermediary value is formed by approximation.
If controlled variable R does not reflect all the relevant influences for ascertaining the required duty factor, for example, via a temperature variation, different implementation of the circuit which is controlled by the manipulated variable, or the like, the characteristics map must be parametrizable. This is achieved by implementing all values F(RN) as programmable parameters in a memory (RAM) or by keeping a plurality x of characteristics maps Fx(RN) as constants in a non-volatile memory (ROM) in the hardware and selecting the required characteristics map via a programmable parameter.
Conventional circuits for implementing characteristics maps require a high degree of hardware complexity. An object of the present invention is therefore to optimize the hardware implementation of a parametrizable characteristics map in such a way that a small number of programmable parameters and constants are needed, while high mapping accuracy is achieved, thus reducing the hardware complexity and the costs.